Thermal-Cycling Durability of Printed Photopolymers and Hybrid Assemblies: Expansion Mismatch, Interface Damage and Property Drift

Thermal cycling is not equivalent to storage at one elevated temperature. Each excursion changes modulus, thermal strain, moisture state and residual stress; repeated reversals can accumulate interfacial slip, crazing, microcracking, warpage and loss of preload even when neither temperature extreme causes immediate failure. Printed photopolymers add cure gradients, orientation, layer structure and post-processing history to this problem. Hybrid assemblies add coefficient-of-thermal-expansion mismatch among resin, fillers, coatings, inserts, adhesives and fasteners.

This review establishes a non-compensatory framework for thermal-cycling qualification. It requires the real part temperature and dwell history, not chamber setpoints alone; separates irreversible post-cure or physical ageing from reversible temperature response; treats ramps, dwells and transitions as independent stressors; and links dimensional, mechanical, thermal and interfacial measurements to a declared service claim. A single glass-transition temperature, heat-deflection temperature or successful visual inspection cannot release a cycling claim. Qualification requires state-matched controls, intermediate inspections, failure-mode attribution, residual-property measurements and a prospective holdout profile. Published photopolymer evidence supports strong temperature and post-cure dependence, but direct, generalisable thermal-cycle datasets remain limited. The defensible output is therefore an application-bounded durability envelope, not a universal number of cycles.

Keywords: printed photopolymer; thermal cycling; coefficient of thermal expansion; residual stress; interface damage; post-cure; warpage; durability qualification